It can be used but we recommend being cautious with dosage with needling to the effected area. CRPS is a central disorder so you need to be careful to how the patient may respond. I would start with sensory needling proximal to the affected area. I would also consider the associated paravertebral points for the involved area.
Here are some links to a couple of peer reviewed publications. Small sample size in the one and the other a case study but they are using DN in support of CRPS.
https://www.ncbi.nlm.nih.gov/pubmed/26752485
https://www.ncbi.nlm.nih.gov/pubmed/26752490
